The general objective of the 5-year continuation of our research program is the development of a comprehensive and systematic study of the neuronal organization of the cerebellar-brain stem system and its relation to the coordination of movement. The research will continue to stress a comparative approach. The basic philosophy of the overall experimental design is, fundamentally, a multidisciplinary one; different techniques and areas of knowledge will be amalgamated to determine the morphological and functional properties of single cells, their neuronal circuits, and their ionic micro-environment. Different electrophysiological and biophysical techniques including intra- and extracellular recordings of single cell activity, field potential and current density analysis, ion sensing electrode techniques and intracellular marking with different dyes will be used. Physiological stimuli (visual, vestibular, and joint movement) will be utilized in most paradigms. The morphological studies will utilize light and electron microscopy and computer-aided reconstruction. The electrophysiological and morphological data will be combined to generate computer models in order to further relate the functional properties of single cells to their actual structure. Eye movement-related experiments will be performed in both anesthetized and unanesthetized preparations. Special computer techniques will be used to relate particular parameters of these movements to the activity of the above circuits. Pharmacological tools will be used, when necessary, to clarify functional points concerning the properties of single cells or of special neuronal circuits.